Custom connector only offers OAuth fields for an API-key-authenticated MCP server (Deckbase) — no "Request headers" option available

### MCP server URL or name

https://www.deckbase.co/api/mcp

### How are you connecting to this server?

From a custom connector URL I entered manually

### Where does the issue occur?

When pressing the Connect button

### When did you last reproduce this?

2026-08-02, 17:30 CEST

### Browser and OS

Claude Desktop app on Windows 11 Pro (not browser-based)

### Describe the issue

I'm trying to connect Deckbase (a flashcards app) as a custom connector via its remote MCP server. Deckbase authenticates via a static API key sent as an "Authorization: Bearer " header, not OAuth. When adding it through Customize > Connectors > Add custom connector, the "Advanced settings" section only shows fields for "OAuth Client ID" and "OAuth Client Secret" — there is no "Request headers" field available on my account. When I click Connect, Claude attempts an OAuth flow anyway, which fails because Deckbase's server has no OAuth client registered.

### Error details

```shell
Claude.ai showed a generic connection failure after clicking Connect.
The browser tab opened by the OAuth redirect showed:
{
"error": "invalid_client",
"error_description": "Unknown client_id"
}
```

### Expected behavior

Since Deckbase (and presumably other MCP servers using simple API-key auth) doesn't implement OAuth, I'd expect to be able to authenticate via a static header (e.g. Authorization: Bearer ) when adding a custom connector — either because this is generally available, or because my account gets access to the header-authentication beta mentioned in Claude's documentation.

### Additional context

I've confirmed with Deckbase support that their MCP server only supports API-key/Bearer token auth, with OAuth not currently planned. My account's "Add custom connector" dialog shows only OAuth Client ID/Secret fields, suggesting the header-based auth beta hasn't rolled out to my account yet.